Obstruct, snooker (6)
I believe the answer is:
stymie
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">obstruct</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">snooker</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(both can mean to frustrate or hinder)</span><br/ ><br/ ></span>
(Other definitions for stymie that I've seen before include "Hinder the progress of (something)" , "Tricky situation" , "Block or thwart, say a golf putt" , "Thwart, foil" , "Obstruct as on putting green" .)